Copying machine with capacity to measure transparency of original

Abstract

A copying machine of the present invention measures light transmittance of a document so as to adjust copying concentration on the basis of the measured result. The copying concentration is concretely adjusted by adjusting electrification voltage of a photosensitive body, and/or developing bias voltage, and/or quantity of exposure light. The copying machine is free from the occurrence of back image copying when a document is double-faced. A copying machine of the present invention further comprises means for discriminating whether the document is a double-faced one or a single-faced one.

What is claimed is: 
     
       1. A copying machine irradiating light to a document from an exposure light source, guiding the reflected light from said document to a photosensitive body so as to form latent images corresponding to images of said document, supplying toner from a developing unit so as to develop said latent images, and transferring said developed images onto a copying paper, comprising: measuring means for measuring light transmittance of said document, said measuring means using said exposure light source as its light source when the light transmittance of said document is measured; and   adjusting means for adjusting a copying condition corresponding to said light transmittance measured by said measuring means.   
     
     
       2. A copying machine according to claim 1, wherein said adjusting means adjusts quantity of light from said exposure light source. 
     
     
       3. A copying machine according to claim 1, wherein said adjusting means adjusts the electrification voltage of said photosensitive body. 
     
     
       4. A copying machine according to claim 1, wherein said adjusting means adjusts the developing bias voltage. 
     
     
       5. A copying machine according to claim 1, further comprising discriminating means for discriminating whether said document is a double-faced document or a single-faced document. 
     
     
       6. A copying machine according to claim 5, wherein said measuring means measures the light transmittance of said document, when said discriminating means discriminates said document is double-faced. 
     
     
       7. A copying machine according to claim 5, wherein said discriminating means discriminates whether said document is double-faced or single-faced corresponding to light reflectance at both faces of said document. 
     
     
       8. A copying machine according to claim 1, further comprising feeding means for automatically feeding said document toward an exposure position. 
     
     
       9. A copying machine according to claim 8, wherein said measuring means starts operation in accordance with start of operation of said feeding means. 
     
     
       10. A copying machine according to claim 8, further comprising discriminating means for discriminating whether said document is double-faced or single-faced. 
     
     
       11. A copying machine according to claim 1, wherein said exposure light source scans said document. 
     
     
       12. A copying machine according to claim 11, wherein said measuring means scans said document together with said exposure light source. 
     
     
       13. A copying machine according to claim 2, wherein said measuring means uses said means for illuminating as a light source when the light transmittance of said document is measured. 
     
     
       14. A copying machine for copying images of a document onto a copying paper with variable copying concentration, comprising: a photosensitive body;   means for illuminating said document;   means for projecting the reflected light from said document onto said photosensitive body to thereby form electrostatic latent images;   means for changing said electrostatic latent images on said photosensitive body to visible images;   means for transferring onto said copying paper said visible images on said photosensitive body;   detecting means for detecting whether or not images exist at both faces of said document;   measuring means for measuring light transmittance of said document; and   means for deciding an optimum copying concentration on the basis of the measured light transmittance only when said detecting means detects that images exist at the both faces of said document.   
     
     
       15. A copying machine according to claim 14, said detecting means including means for measuring light reflectance of both faces of an original. 
     
     
       16. A copying machine irradiating light to a document from an exposure light source, guiding the reflected light from said document to a photosensitive body so as to form latent images corresponding to images of said document, supplying toner from a developing unit so as to develop said latent images, and transferring said developed images onto a copying paper, comprising: means for inputting copying concentration;   measuring means for measuring light transmittance of said document, said measuring means using said exposure light source as its light source when the light transmittance of said document is measured;   means for deciding an optimum copying concentration on the basis of the measured light transmittance, and   means for controlling the copying operation with either of the inputted copying concentration and the decided optimum copying concentration.   
     
     
       17. A copying machine for copying images of a document onto a copying paper with variable copying concentration, comprising: a photosensitive body;   feeding means for automatically feeding said document toward an exposure position;   means for illuminating said document at said exposure position;   means for projecting the reflected light from said document onto said photosensitive body to thereby form electrostatic latent images;   means for changing said electrostatic latent images on said photosensitive body to visible images;   means for transferring onto said copying paper said visible images on said photosensitive body;   detecting means for detecting whether or not images exist at both faces of said document;   means responsive to said detecting means for controlling said feeding means;   measuring means for measuring light transmittance of said document; and   means for deciding an optimum copying concentration on the basis of the measured light transmittance only when said detecting means detects that images exist at both faces of said document.   
     
     
       18. A copying machine according to claim 15, said detecting means including means for measuring light reflectance of both faces of an original. 
     
     
       19. A method of obtaining light transmittance of a document, comprising: a first step of measuring light reflectance of one face of the document;   a second step of measuring light reflectance of the other face of the document;   a third step of measuring light transmittance of the document when the measured light reflectance of one face of the document is larger than a first predetermined value and the measured light reflectance of the other face of the document is larger than a second predetermined value, and   a fourth step of storing the measured light transmittance of the document into a memory.